The invention relates to an institutional or industrial warewashing detergent and to its use in automatic warewashing machines that operates with a wash and a rinse cycle. The detergent of the invention promotes soil removal and rinsing or rinse water sheeting in washing and rinsing stages, respectively. The detergent can include a cleansing source of alkalinity, a rinsing source of nonionic and can contain additional ingredients such as surfactants, rinse agents, builders, hardness sequestering agents, etc.
A variety of warewashing detergents have been in common use in wash water solution at high temperature (temperature sanitizing) or low temperature (chemical sanitizing) for many years in both institutional and household automatic warewashing machines. Such detergents have taken the form of a thickened liquid, particulate solid, a pellet, aqueous solution or dispersion or in the form of a solid block detergent. In institutional warewashing, such particulate, pellet or solid block detergents are dispensed using an automatic dispenser that creates an aqueous concentrate (i.e.) an aqueous solution or suspension of the alkaline detergent using a water spray. The water spray dissolves a portion of the detergent when needed to for the aqueous concentrate. The aqueous concentrate is directed into a washing chamber in the automatic warewashing machine for a wash cycle. Such detergents have been based on a variety of sources of alkalinity including alkali metal hydroxide, alkali metal silicate, alkali metal carbonate or bicarbonate, etc.
During the wash cycle, the organic or inorganic components of the aqueous warewashing detergent effectively remove soil from ware. Detergent additives provide other functionality to the detergent such as water treatment, defoaming, etc. After cleaning with the detergent, the ware is commonly rinsed using an aqueous rinse composition made through the intentional combination of a rinse agent and an aqueous diluent. An aqueous rinse composition typically comprises a major proportion of water and about 50 to 400 parts of an active rinse agent per million parts of the rinse water. Rinse agents are commonly nonionic surfactants that adjust the surface energy of the ware with respect to the water to promote sheeting and complete rinse water removal. Ware free of rinse water can then dry without spotting or streaking. In typical detergent processing, the use of a water rinse without a rinse agent typically produces ware having substantial streaking and spotting caused by aqueous residue derived from the rinse remaining on the dishes after the rinse cycle ends.
In an institutional automatic warewashing machine, rinse agents and alkaline detergents are intentionally added separately using dispensers designed for either a specific rinse agent or a detergent. As set forth below, rinse agents are primarily nonionic surfactant material. Rinse agents are typically a subset of the alkylene oxide polymeric nonionic materials and have unique properties that promote sheeting action in rinse water to avoid spotting and streaking. Not all nonionic materials are appropriate for rinsing use. Rinse agents should change the energy at the interface between the washed ware and the rinse water such that the rinse water is removed completely from the surface of the ware. Such as interface energy must be reduced to prevent the adhesion of water droplets to the washed ware surface. Further, rinse agents should be low foaming to prevent machine pump cavitation caused by high levels of foam.
Automatic warewashing machines used in a variety of institutional and industrial locations come in a large variety of embodiments. The simplest machines are typically machines operating at low temperature (less than 160xc2x0 F.) having a single tank for aqueous materials used in the wash cycle. Such low temperature machines typically use a washing cycle that uses a washing solution prepared from an alkaline detergent composition. Once the short washing cycle is complete, the washing liquid is typically dumped from the machine and the ware is rinsed using a rinse cycle. The rinse water is typically maintained in the machine for reuse in the next wash cycle. To create a proper wash water material, additional detergent is typically dispensed into the water to restore the appropriate concentration of the washing ingredient components. After the wash to washing and rinsing cycles are complete, the ware can be contacted with the sanitizer material to ensure complete safety. Larger multistation high temperature machines (greater than about 160xc2x0 C.) are also used in locations having a higher volume of ware cleaning. Such machines typically involve a conveyor system in which individual racks of ware are moved through the multistation machine for a complete washing regimen. Often such ware racks are prescrubbed to remove large gross soils in a prewasher/prescrape stage, the ware is contacted with water under pressure to remove all large food items prior to washing. In the large rack conveyor systems, the ware and rack are typically exposed to a prewash stage, a power wash stage, a power rinse stage, a final rinse stage and can be exposed to a blow dryer to complete the production of a clean dry dish. Prewash stage is often involved contacting the ware with aqueous streams containing moderate amounts of cleaner materials to clean or prepare soils for removal. In a power wash stage, the ware is contacted with aqueous detergents containing effective concentrations of alkaline materials, surfactants and other components to completely remove the soils and prepare for the power wash stage in the prewash stage. The ware is then often directed to a power rinse stage and a final rinse stage. In these rinse stages, the alkaline detergent materials are rinsed from the dishes and if necessary, the ware can be exposed to a sanitizer rinse. In order to ensure that no confusion results from the discussion of the warewashing machines, simple dump and fill, single zone dishwashers can be operated at both high and low temperature. Similarly, large conveyor systems can also be operated at high or low temperature. These warewashing machines can also have a variety of other elements including conveyor units, drive units, storage locations, waste system disposals, racks, etc. Further, the reuse or recycling of rinse water is also common in both high and low temperature machines. The relatively clean rinse water that remains after rinsing is complete is often recycled to a wash tank for the purpose of creating a wash solution using an alkaline concentrate containing the wash chemicals.
Rinse agents used in machine rinse cycles have a polymer composition that is optimized to provide rinsing properties that have relatively reduced surfactancy, soil removing properties or other properties common to nonionic materials in general. A conventional rinse agent is typically formulated as a concentrate in liquid or solid form which is diluted with water in a rinse aid dispenser to form an aqueous rinse composition used in a warewashing machine rinse cycle to ensure that dishes sheet cleanly. The requirement for a separate rinse dispenser adds additional expense and complexity to institutional warewashing machines. This is particularly true in smaller low temperature machines having a single station that is used for all cycles in a warewashing regimen. In the low temperature machine, a rinse cycle follows a wash cycle and the rinse water is typically retained, combined with detergent and used in the washing cycle. After the washing cycle is complete the water is then directed to a machine drain. Low temperature machines are typically used in relatively small volume warewashing locations. Such locations require relatively simple operating machines with minimal moving parts and minimal upkeep and maintenance. Larger installations, having conveyor type machines that clean a large volume of ware, often on a 24 hour a day basis, also have a need for an easily used warewashing machine and warewashing chemicals. Accordingly a need has existed in this art to reduce the amount of chemicals stored and used in warewashing locations using either a relatively simple low temp machine or a relatively complex high temp conveyor-type machine.
We have found that institutional or industrial warewashing detergents adapted for use in automatic warewashing machines can be formulated with a critical amount of a rinse agent composition in the warewashing formulation, to provide sheeting and rinsing in a subsequent potable water rinse cycle. In this rinse cycle nonionic rinse agents are intentionally omitted from the aqueous rinse composition. Residual nonionic surfactants left on the ware, rack and machine surfaces dissolve in the rinse water to promote rinse sheeting. This detergent is adapted primarily for use in a machine that uses no separate rinse aid or dispenser. However, the detergent can be used with a typical aqueous rinse composition. Surprisingly, we have found that above the critical concentration of rinse agent in the warewashing detergent, a sufficient quantity of rinse agent material to cause rinse sheeting carries over on the wet dishes, rack and on the machine internal working parts, after the cleaning cycle is complete. The residual rinse aid can promote adequate sheeting in the potable water rinse cycle to substantially remove rinse water from the dishes leaving the dishes substantially spot-free. The potable water rinse is typically formulated with no intentionally added rinse agent. The use of such a detergent rinse agent combination permits operators to avoid the complexity or expense of both a separate rinse agent dispenser and purchasing rinse agent, if desired. The resulting operations are surprisingly efficient, produce clean, spot and streak-free dishes and can reduce both personnel and materials costs. In addition, the high surfactant level in the wash cycle enhances the removal of greasy soils which in turn creates a surface which is easier to rinse sheet and dry free of films and spots.
Typical useful rinse agents are the poly (lower alkylene oxide) polymers that are usually prepared by the condensation of lower (2-4 carbon atoms) alkylene oxide monomer (s) that have rinsing or sheeting activity. For example, ethylene oxide or propylene oxide (with enough ethylene oxide to make a water soluble or dispersible product), can be condensed with a compound having a hydrophobic hydrocarbon chain and containing one or more active hydrogen atoms such as a higher alkyl phenol, higher fatty acids, higher fatty amines, higher fatty polyols and alcohols and in some cases higher fatty mercaptans. Such compounds include fatty alcohols having 8-20 carbon atoms in an alkyl or aliphatic chain, an alkoxylate (preferably ethoxylate) with an average of about 1 to 100, preferably 5 to 20 with 2 to 25, 5 to 20 lower alkylene oxide moieties. Preferred nonionic materials are those represented by the formula:
RO(C2H4O)nxe2x80x94H
wherein R is the aliphatic or alkyl saturated residue having 5 to 100 carbon atoms and n is a number from 5 to 25.
The aqueous cleaning composition comprising a major proportion of an aqueous diluent and about 250 to 3000 and typically 800 to 1800 parts by weight of an alkaline warewashing detergent per each one million parts of the aqueous diluent. The detergent includes about 0.1 to 60 wt-% of a source of alkalinity, and at least about 30 wt-% of nonionic surfactant having at least one block segment comprising -(AO)x- where AO represents an oxyalkylene moiety and x is a number of about 1 to 100.
Morganson et al., U.S. Pat. No. 5,080,819 and Gansser, U.S. Pat. No. 4,753,755, teach an alkaline solid block detergent containing a small, but effective amount of a nonionic surfactant to aid in soil removal at typical warewashing temperatures. Morganson et al. teach that aqueous washing solutions containing alkaline materials such as carbonates, silicates, etc. often fail to clean completely at low temperatures. The nonionic surfactant in these systems provide extra soil removal properties. Gansser, U.S. Pat. No. 4,753,755 teaches broadly a warewashing detergent having from 10-90 wt % of a nonionic material. Neither Gansser nor Morganson et al. indicate that a rinse agent nonionic can be added to a low alkaline cast solid to act as a rinse agent nor does Gansser or Morganson et al. teach any particular utility for such a rinse aid material in a solid detergent. Nonionic materials adapted for detergent purposes are typically different than rinse agent materials.
Conventional alkaline detergents are disclosed in Fernholz et al., U.S. Pat. Nos. 4,569,780 and 4,569,781; Heile et al., U.S. Pat. Nos. 4,595,520 and 4,680,134; Olson et al., U.S. Pat. No. 4,681,914; Gansser, U.S. Pat. No. 4,753,755; Copeland, U.S. Pat. No. 4,725,376; Lokkesmoe et al., U.S. Pat. No. 4,793,942; Killa, U.S. Pat. No. 4,846,989; Lentsch et al., U.S. Pat. No. 4,861,518; Morganson et al., U.S. Pat. No. 5,080,819; and Gladfelter et al., U.S. Pat. No. 5,316,688.
Conventional rinse agents are disclosed in Copeland, U.S. Pat. No. 4,594,175; Morganson et al., U.S. Pat. No. 4,624,713; Copeland, U.S. Pat. No. 4,711,738; Gladfelter et al., U.S. Pat. No. 5,358,653; Steindorf, U.S. Pat. No. 5,447,648; Copeland et al., U.S. Pat. No. 4,938,893; and also see Mizuno et al., U.S. Pat. No. 3,166,513; Sabatelli et al., U.S. Pat. No. 3,535,258; Sabatelli et al., U.S. Pat. No. 3,579,455; Mizuno et al., U.S. Pat. No. 3,700,599 and Copeland et al., U.S. Pat. No. 3,899,436. Dispensers for creating an aqueous rinse by combining diluent water with a rinse agent are shown in (e.g.) Fernholz, U.S. Pat. No. 5,320,118; Copeland, U.S. Pat. No. 4,690,305; Copeland, U.S. Pat. No. 4,687,121; Copeland et al., U.S. Pat. No. 4,826,661; and Copeland, U.S. Pat. No. 4,999,124.